{"apiVersion":"1.0","identifier":"CVE-2026-74284","description":"In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_hfsc: Don-t make class passive twice update_vf() is called from two places for the same class during a single dequeue when the class-s child qdisc (e.g. codel/fq_codel) drops its last packets while dequeuing: 1. The child calls qdisc_tree_reduce_backlog(), which, now that the child is empty, invokes hfsc_qlen_notify() -> update_vf(cl, 0, 0) and turns the class passive (cl_nactive is decremented up the hierarchy). 2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time) to charge the dequeued bytes. On the second call the class is already passive, but its child qdisc is still empty, so update_vf() arms go_passive again: if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC) go_passive = 1; The leaf is then skipped by the cl_nactive == 0 check inside the loop, which does not clear go_passive, so the stale go_passive propagates to the parent and decrements its cl_nactive a second time. A parent that still has other active children is driven to cl_nactive == 0 and removed from the vttree, even though those siblings are still backlogged. They are never dequeued again and the qdisc stalls. Fix this by only arming go_passive when the class is actually active, so an already-passive class no longer triggers a second passive transition. The byte accounting (cl->cl_total += len) still runs for every ancestor, so dequeued bytes continue to be counted exactly once.","publishedAt":"2026-08-15T06:22:27","lastModifiedAt":"2026-08-17T06:19:22","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-74284","cvssScore":null,"cvssVector":"Pending","epssProbability":0.00216,"riskScore":0,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-74284","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-74284","en":"https://www.redsauce.net/en/cves/CVE-2026-74284","fr":"https://www.redsauce.net/fr/cves/CVE-2026-74284","pt":"https://www.redsauce.net/pt/cves/CVE-2026-74284","de":"https://www.redsauce.net/de/cves/CVE-2026-74284","sk":"https://www.redsauce.net/sk/cves/CVE-2026-74284","el":"https://www.redsauce.net/el/cves/CVE-2026-74284"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-74284"}}